Two area bridges crossing the Mississippi River are scheduled to start construction on upgrades in the next week, one in Iowa and one in Minnesota.

In Dubuque Iowa authorities are preparing to temporarily close down a bridge that connects Iowa with Illinois.

The Telegraph Herald reports the Julien Dubuque Bridge is scheduled to close for repairs beginning Monday. It is set to be completed on July 31.

The bridge connects Dubuque and East Dubuque, Illinois. Iowa drivers will be detoured across the Dubuque-Wisconsin bridge to then enter Illinois. The pedestrian and bike trail on the bridge will remain open during construction.

Work on the structure will involve replacing deck joints, removing a 6-foot span of the bridge and sealing the barrier rail. The newspaper reports residents and business are bracing for expected traffic delays, lost sales and other costs.

In Minnesota a number of area leaders and transportation officials gathered in Winona today for a groundbreaking on a new bridge to stand along side the exiting Mississippi Bridge.

The bridge will cost about $162 million, with $91 million in federal dollars and the rest from state and local sources.

Work will take about about five years, but planning has been going on much longer.

The existing bridge opened in 1942 and has a fracture-critical design, meaning if one major beam or part fails, the whole bridge could fall. The new one will have redundant systems, so failure of one part won’t be as potentially catastrophic.

A push for a new bridge began in earnest after the 2008 collapse of the Interstate 35W bridge across the Mississippi in Minneapolis, which killed 13 people and injured many more. That bridge was also fracture-critical, and some gusset plates failed. That prompted the Minnesota Department of Transportation to begin looking at similar bridges.

In Winona, MnDOT found cracks and major deterioration in gusset plates that held together the beams holding up the deck. The bridge was closed, even though many people used it daily.

People who needed the bridge had to drive to Wabasha or La Crosse, Wis., to cross the river. The city also set up a ferry system to get people across as MnDOT began work on replacing some of the worst plates.

Eventually, the bridge was reopened and the plates repaired, but the closing pushed up the timeline for a complete rehabilitation or replacement.

MnDOT chose not to tear down the old bridge because it’s historic. Planners for the city and state also had to figure out how to connect the new bridge to Winona. The bridge comes into Winona near the downtown, and there is a major traffic headache there.

Eventually, MnDOT decided to build a new two-lane bridge for westbound traffic and rehabilitate the old one for eastbound traffic.

Here is a very cool computer simulation done by the Minnesota DOT of what the new bridge will look like.